1. Technical Field
The invention relates to an integrated circuit arrangement, and more particularly, to an integrated circuit arrangement having an electrically conductive conduction structure and a layer stack arranged between the conduction structure and a dielectric at a side wall of the conduction structure.
2. Background Information
The conduction structure includes, for example, an interconnect for lateral current transport or a via for vertical current transport. In this context, the term lateral means parallel to a main surface of a substrate of the circuit arrangement, a multiplicity of integrated semiconductor components being arranged in the main surface. The term vertical means in the normal direction or opposite to the normal direction to the main surface. The conduction structure consists, for example, of copper or a copper alloy. What is known as the single Damascene process or what is known as the dual Damascene process is used in conjunction with copper conduction structures. The conduction structures are embedded in a dielectric, for example in silicon dioxide or a dielectric with a low relative dielectric constant of, for example, less than 3.9 or less than 3.
Layer stacks are used to prevent diffusion of the copper into the dielectric and then into a single-crystal semiconductor substrate, and these layer stacks are also intended to ensure good mechanical bonding between the dielectric and the conduction structure. In a Damascene process, the copper conduction structure is produced using an electrolytic process, for example with a layer thickness of greater than 100 nm. The electrolytic process is carried out using external current, the layer stack being used for current conduction, for example because a fixed potential, which is the opposite potential to a counterelectrode connected as anode, is applied to the edge of the wafer.
Processes for producing ultrathin multilayer stacks and multilayer stacks which overall serve both as reliable bonding layers, as diffusion barriers and also as layers for homogeneous and spontaneous seeding of subsequent chemical vapor deposition (CVD) or electrochemical deposition (ECD) deposition of metal, should which satisfy the thickness requirements of the International Technology Roadmap for Semiconductors (ITRS) 2003, Update 2004, for future technologies. Even with very large wafer diameters (for example 300 mm or above), the multilayer stacks allow homogeneous deposits which form a void-free filling in single or dual Damascene structures with a high aspect ratio, e.g. of greater than one. In particular, deposition of Cu or W by electrolytic, electroless or metalorganic CVD (MOCVD) processes becomes possible. Any surface oxide which may form—unlike in the case of Cu seed layers—will not cause problems and will not lead to fillings which contain voids.
Ultrathin layer combinations of type A/B/A, A/B/A/B/A, A/B/A/B/A/B/A, or A/B/A′, A/B/A′/B/A or A′, etc., have the properties mentioned, wherein: conduction layer materials A represent, for example, ruthenium (Ru), tungsten (W), rhodium (Rh), rhenium (Re), molybdenum (Mo) or alloys thereof or similar materials; and conduction layer materials A′ represent, for example, ruthenium (Ru), tungsten (W), rhodium (Rh), rhenium (Re), molybdenum (Mo), copper (Cu), silver (Ag), gold (Au), palladium (Pd), platinum (Pt) or alloys thereof or similar materials. Examples of suitable A′ materials also include nickel (Ni), chromium (Cr) or cobalt (Co), in particular if the material B arranged below is in elemental form, i.e. contains only one type of atom. Interlayer materials B represent, for example, Ta, TaN, a double layer TaN/Ta, TaC, TaCN, TaSiN, WN, WC, WCN, WSiN, TiN, TiC, TiCN, TiSiN, Al, Cr, Ni, Co, Pd, Pt, C or alloys thereof or similar materials.
Pure Ru layers with a thickness of 20, 30 or 40 nm, on account of their columnar structure, are not adequate Cu diffusion barriers, and therefore require additional barrier layers, by way of example the A/B/A/B/A layer combination with A≦5 nm Ru and B≦2 nm TaN does constitute a sufficient Cu diffusion barrier.
The materials of group A are typically low-resistance refractory metals, i.e. metals with a melting temperature of greater than 1600° C. or even greater than 2000° C. The group A′ is a wider group than group A because of the addition of low-resistance semi-precious metals, e.g. Cu, or low-resistance precious metals. The term low-resistance means that the resistivity is ρ≦50 μΩ cm or ρ≦20 μΩ cm, measured for example on a material in bulk form, for example a layer with a thickness of 200 nm or greater. The materials of group A or A′ often cannot be alloyed or mixed with Cu or other interconnect materials. The minimum thickness required for the A materials or A′ materials is determined by the sheet resistance which is still permissible during the subsequent electrolytic deposition of Cu and by the number of A layers or A′ layers. To produce effective diffusion barriers, it has proven particularly advantageous for the deposition process used to deposit the A component or A′ component to be interrupted one or more times and for extremely thin (≦2 nm) layers or processes of the B components to be introduced at least once.
The materials of group B are typically conductive layers with a Cu diffusion barrier action. Because of their own conductivity, they also contribute to the conductivity of the layer stack and therefore to its function as a seeding layer for subsequent deposition processes which require a certain minimum conductivity. However, the contribution of the B components to the barrier action is even more important. Not only do they have a diffusion-inhibiting action themselves, but also, they modify the growth of the subsequent A component or A′ component. Whereas the latter preferentially grow in columnar form in thicker single layers, the intercollation of thin and therefore often amorphous B components brings about initially likewise amorphous incipient growth of the A components or A′ components. Unlike the A components or A′ components in columnar form, the corresponding amorphous or X-ray amorphous A species or A′ species likewise make a contribution to the barrier action.